Electric fan for outdoor use

ABSTRACT

An electric fan includes a base, a drive unit, a fan blade, and a direct current power source. The drive unit is mounted on the base, and includes a direct current fan motor and an electrical socket connected to the fan motor. The fan blade is coupled to and is driven rotatably by the fan motor. The direct current power source is coupled electrically to the fan motor, and includes a storage battery and an electrical plug connected to the storage battery. When the electrical socket and the electrical plug are interconnected, the storage battery provides power to the fan motor for operation of the electric fan.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to an electric fan, more particularly to an electric fan suitable for outdoor use.

[0003] 2. Description of the Related Art

[0004] A conventional electric fan includes a base, a fan motor mounted on the base, and a fan blade coupled to and driven rotatably by the fan motor. The fan motor has a power cable terminated by an electrical plug that is to be plugged into a commercial alternating current power source so as to enable the fan motor to drive the fan blade to rotate for ventilation purposes.

[0005] Due to the requirement of connection to the alternating current power source, the aforesaid electric fan is limited for use in locations where electrical outlets are available, and is thus not suitable for outdoor use. Moreover, the length of the power cable imposes restrictions on the distance of the electric fan from the power source.

SUMMARY OF THE INVENTION

[0006] Therefore, the object of the present invention is to provide an electric fan having a direct current fan motor powered by a direct current power source so as to overcome the aforesaid drawbacks associated with the prior art.

[0007] Accordingly, an electric fan of this invention comprises a base, a drive unit mounted on the base and including a direct current fan motor, a fan blade coupled to and driven rotatably by the fan motor, and a direct current power source coupled electrically to the fan motor.

[0008] Preferably, the drive unit further includes a first cable connected electrically to the fan motor and terminated by an electrical socket, and the power source includes a second cable terminated by an electrical plug that is connected removably to the electrical socket, and a storage battery connected electrically to the second cable.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which:

[0010]FIG. 1 is a perspective view of the preferred embodiment of an electric fan according to the present invention;

[0011]FIG. 2 is another perspective view of the preferred embodiment in a state ready for use; and

[0012]FIG. 3 is a schematic electrical circuit diagram of the preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] Referring to FIGS. 1 to 3, the preferred embodiment of an electric fan according to the present invention is shown to include a base 30, a drive unit 10 mounted on the base 30, a fan blade 20 coupled to and driven rotatably by the drive unit 10, and a direct current power source 40.

[0014] The drive unit 10 includes a direct current fan motor 19, a first cable 121 connected electrically to the fan motor 19 and terminated by an electrical socket 12, and a known positioning unit 13 for locking releasably rotation of the drive unit 10 relative to the base 30 about a vertical axis. Particularly, when a knob of the positioning unit 13 is depressed, the drive unit 10 can rotate about the vertical axis, and when the knob of the positioning unit 13 is lifted, the drive unit 10 can be prevented from rotating about the vertical axis. A speed control unit 18 is coupled electrically to the fan motor 19, and has a control knob 11 that is manually operable so as to adjust output speed of the fan motor 19. As best shown in FIG. 3, the speed control unit 18 includes a variable resistor 14 having a resistance that is adjusted under the control of the control knob 11, a voltage comparator 15 having an output voltage that varies according to the resistance of the variable resistor 14, a Darlington transistor pair 16 having conducting states controlled by the output voltage from the voltage comparator 15, and a field-effect transistor 17 having a voltage that varies according to the conducting states of the Darlington transistor pair 16. The voltage of the field-effect transistor 17 controls the input voltage of the fan motor 19 and thus the output speed of the fan motor 19.

[0015] The fan blade 20 is coupled to an output shaft of the fan motor 19 in a known manner. Accordingly, manual operation of the control knob 11 can alter the rotating speed of the fan blade 20. A fan guard 50 is mounted on the drive unit 10 and shields the fan blade 20 in a known manner.

[0016] The power source 40 includes a second cable 411 terminated by an electrical plug 41 that is connected removably to the electrical socket 12, and a storage battery 42 connected electrically to the second cable 411. When the electrical plug 41 is connected to the electrical socket 12, the storage battery 42 provides electric power to the fan motor 19 through the cables 411, 121 so as to enable the fan motor 19 to drive rotation of the fan blade 20.

[0017] It has thus been shown that the electric fan of this invention can be operated without the need for connection to an alternating current power source. Accordingly, the electric fan of this invention is not limited for use in premises where electrical outlets are available, and is thus suitable for outdoor use (such as outdoor camping) Moreover, the battery 42 can be easily moved together with the base 30, thus eliminating the restrictions imposed by the power cable in the conventional electric fan.

[0018] It is worth noting that, in actual practice, the preferred embodiment of this invention can utilize a car battery for the power source 40.

[0019] While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements. 

I claim:
 1. An electric fan comprising: a base; a drive unit mounted on said base and including a direct current fan motor; a fan blade coupled to and driven rotatably by said fan motor; and a direct current power source coupled electrically to said fan motor.
 2. The electric fan as claimed in claim 1, wherein said drive unit further includes a speed control unit coupled electrically to said fan motor and having a control knob that is manually operable so as to adjust output speed of said fan motor.
 3. The electric fan as claimed in claim 1, wherein said drive unit further includes a first cable connected electrically to said fan motor and terminated by an electrical socket, and said power source includes a second cable terminated by an electrical plug that is connected removably to said electrical socket.
 4. The electric fan as claimed in claim 3, wherein said power source further includes a storage battery connected electrically to said second cable.
 5. The electric fan as claimed in claim 1, wherein said power source includes a storage battery. 